The present invention relates to a valve, and in particular, to a safety valve which is particularly suitable though not limited to use as a safety valve for controlling the flow of fuel gas to a gas powered appliance, though not limited to such use.
Safety valves which are typically used for controlling the supply of fuel gas to a gas powered appliance, for example, a gas powered heater, a gas powered oven, a gas powered hob or the like, typically comprise a solenoid type operated valve. Such valves comprise a valve housing which define a hollow interior valve chamber. An inlet port is provided to the valve chamber, while an outlet port is provided from the valve chamber. A valve seat is formed within the valve chamber between the inlet and the outlet ports, and defines a communicating passageway between the respective inlet and outlet ports. A valving member located within the valve chamber co-operates with the valve seat for closing the communicating passageway for in turn closing the valve. A solenoid coil co-operable with the valving member when energised urges the valving member out of engagement with the valve seat for opening the communicating passageway for opening the valve. An urging means, typically, a compression spring urges the valving member into engagement with the valve seat when power is removed from the solenoid coil. For safety reasons in general two such solenoid valves are normally located in series in a fuel gas pipeline so that should one of the solenoid valves fail to operate for isolating the gas powered appliance from the fuel gas supply, at least one of the solenoid valves should operate.
In general, the valving member is rigidly secured to a magnetic body of the solenoid coil, so that variation in the intensity of the magnetic field generated by the solenoid coil causes the magnetic body to move and in turn the valving member for opening and closing of the valve. In general, the valving member is spring urged into the closed position, and thus, in order to retain the valve open power must be continuously supplied to the solenoid for so long as it is desired to retain the valve open. Furthermore, the magnetic field generated by the solenoid coil must be of sufficient strength to hold the valving member open against the action of the compression spring which acts to urge the valving member into engagement with the valve seat. This, in general, requires a relatively high current through the solenoid coil which leads to heating of the valve as a result of power dissipation from the solenoid coil which may be as high as 4 watts to 5 watts and in many cases even more. Additionally, such solenoid valves tend to be relatively noisy as the valving member is urged between its open and closed positions.
Accordingly, it is an object of the present invention to provide a valve, and in particular to a provide a safety valve which is particularly suitable for use for fuel gas which overcomes the problems of known types of valves. Although it is also an object of the present invention to provide a valve for other uses which overcomes the problems of known valves.
The present invention is directed towards providing such a valve.
According to the invention there is provided a valve comprising a valve housing defining a valve chamber, the valve chamber forming an inlet chamber and an outlet chamber, a primary valve seat separating the inlet chamber from the outlet chamber and defining a primary communicating passageway communicating the inlet chamber with the outlet chamber, a primary valving member in the valve chamber co-operating with the primary valve seat for selectively closing the primary communicating passageway for isolating the outlet chamber from the inlet chamber, and a drive means for urging the primary valving member out of engagement with the primary valve seat for opening the primary communicating passageway for communicating the respective inlet and outlet chambers, wherein the drive means is releasably magnetically coupled to the primary valving member for urging the primary valving member out of engagement with the primary valve seat, the drive means and the primary valving member being selectively decoupleable, and a first urging means is provided for urging the primary valving member into engagement with the primary valve seat when the primary valving member is decoupled from the drive means.
In one embodiment of the invention a secondary valve seat is located in the outlet chamber downstream of the primary valve seat, the secondary valve seat dividing the outlet chamber into an upstream chamber and a downstream chamber and defining a secondary communicating passageway communicating the downstream chamber with the upstream chamber, and a secondary valving member is provided in the outlet chamber co-operating with the secondary valve seat for closing the secondary communicating passageway for isolating the downstream chamber from the upstream chamber, the secondary valving member being releasably magnetically coupled with the drive means and being urgeable by the drive means out of engagement with the secondary valve seat for opening the secondary communicating passageway for communicating the downstream chamber with the upstream chamber when the secondary valving member is magnetically coupled to the drive means.
In another embodiment of the invention the secondary valving member is selectively decoupleable from the drive means, and a second urging means is provided for urging the secondary valving member into engagement with the secondary valve seat when the secondary valving member is decoupled from the drive means.
In a further embodiment of the invention the secondary valving member is magnetically coupled to the drive means through the primary valving member.
In one embodiment of the invention the secondary valving member is releasably magnetically coupled to the primary valving member.
In another embodiment of the invention the secondary valving member is selectively decoupleable from the primary valving member. Preferably, the secondary valving member is selectively decoupleable from the primary valving member independently of decoupling of the primary valving member from the drive means.
Preferably, the primary and secondary valving members are sequentially urged out of engagement with the respective primary and secondary valving seats by the drive means when the respective primary and secondary valving members are magnetically coupled to the drive means.
Advantageously, the primary valving member is urged out of engagement with the primary valve seat before the secondary valving member is urged out of engagement with the secondary valve seat. Advantageously, the primary valving member is carried on a main carrier member, and the drive means is co-operable with a first secondary carrier member, the first secondary carrier member forming with the main carrier member a magnetic circuit, and a first magnetic field generating means is provided for selectively generating a magnetic field for selectively coupling the main carrier member and the first secondary carrier member.
In one embodiment of the invention a second secondary carrier member is provided for carrying the secondary valving member, the second secondary carrier member forming a magnetic circuit with the main carrier member for facilitating releasable magnetic coupling of the second secondary carrier member with the main carrier member.
In another embodiment of the invention a second magnetic field generating means is provided for selectively magnetically coupling the second secondary carrier member with the main carrier member independently of the magnetic coupling of the main carrier member with the first secondary carrier member.
Preferably, the second urging means acts between the main carrier member and the second secondary carrier member, and advantageously, the secondary valving member is resiliently mounted to the second secondary carrier member for facilitating relative movement between the second secondary carrier member and the secondary valving member for facilitating disengagement of the primary valving member from the primary valve seat prior to disengagement of the secondary valving member from the secondary valve seat.
Preferably, each magnetic field generating means is an electrically powered magnetic field generating means. Advantageously, an electrically conductive connecting means is provided for connecting each magnetic field generating means to an electrical power supply externally of the valve.
In one embodiment of the invention the respective first and second magnetic field generating means are independently connected to the external power supply by the electrically conductive connecting means.
In another embodiment of the invention the first magnetic field generating means comprises a first electromagnetic coil associated with the main carrier member and the first secondary carrier member.
In a further embodiment of the invention the second magnetic field generating means comprises a second electromagnetic coil associated with the main carrier member and the second secondary carrier member.
Alternatively, the first magnetic field generating means selectively couples the second secondary carrier member with the main carrier member.
Advantageously, the first urging means acts between the valve housing and the main carrier member for urging the primary valving member into engagement with the primary valve seat, and preferably, the first urging means comprises a pair of first compression springs.
In one embodiment of the invention the respective first compression springs are electrically conductive and are electrically mutually insulated for acting as the connecting means for connecting the first magnetic field generating means to the external electrical power supply.
In an alternative embodiment of the invention the respective first compression springs independently connect the respective first and-second magnetic field generating means to the external electrical power supply.
In one embodiment of the invention the first compression springs are concentrically mounted. Preferably, the second urging means comprises a second compression spring.
In one embodiment of the invention the valve chamber is an elongated chamber, and the main carrier member is an elongated member extending longitudinally in the valve chamber through the primary communicating passageway from the inlet chamber to the outlet chamber. Preferably, the valve chamber is of circular transverse cross-section defining a main longitudinally extending central axis, and the main carrier member is located co-axially with the main central axis. In one embodiment of the invention the inlet chamber is of transverse cross-sectional area greater than that of the outlet chamber, and the primary valve seat is formed by a step change in the cross-sectional area of the valve chamber between the outlet chamber and the inlet chamber.
In another embodiment of the invention the transverse cross-sectional area of the upstream chamber is greater than that of the downstream chamber, and the secondary valve seat is formed by a step change in the cross-sectional area of the outlet chamber between the downstream and the upstream chambers.
In one embodiment of the invention the valve housing defines an open mouth to the valve chamber of transverse cross-sectional area sufficient to accommodate the primary and secondary valving members into the valve chamber, and an end cap sealably engageable with the valve housing closes the open mouth.
In another embodiment of the invention the primary valving member extends around the main carrier member. Advantageously, the first and second secondary carrier members are located at respective opposite ends of the main carrier member.
In one embodiment of the invention the drive means comprises a drive motor, and a screw drive transmission between the drive motor and the first secondary carrier member. Preferably, the drive shaft of the drive motor is threaded for engaging a correspondingly threaded bore in the first secondary carrier member for forming the screw drive transmission. Advantageously, the drive motor and the screw drive transmission define a rotational axis which coincides with the main central axis of the valve chamber.
In one embodiment of the invention a keying means keys the first secondary carrier member is keyed in the valve chamber for preventing rotation thereof as the screw drive transmission rotates for urging the first secondary carrier member longitudinally along the main central axis.
In one embodiment of the invention a main outlet port is located in the valve housing communicating with the downstream chamber of the outlet chamber, and advantageously, a secondary outlet port is provided in the valve housing communicating with the upstream chamber of the outlet chamber, and ideally, an inlet port is provided in the valve housing communicating with the inlet chamber.
Ideally, the drive motor is provided by a stepper motor, and preferably, comprises a permanent magnet rotor keyed to the drive transmission, the rotor being located in the valve chamber, and a stator comprising a plurality of electromagnetic stator coils being located radially around the rotor and being sealably isolated from the rotor. Advantageously, the stator coils are located in the end cap.
In one embodiment of the invention the valve is adapted for controlling the flow of a fluid therethrough.
In another embodiment of the invention the valve is adapted for controlling the flow of gas therethrough.
In a further embodiment of the invention the valve is adapted for controlling the flow of fuel gas therethrough.
In a still further embodiment of the invention the secondary outlet port is adapted for connecting to a pilot light jet of a gas powered appliance, and the main outlet port is adapted for connection to a main burner of the gas appliance.
The advantages of the invention are many. A particularly important advantage of the invention is that the valve according to the invention is particularly suitable as a safety valve for use in supplying fuel gas to a gas appliance. In particular the valve according to the invention provides an on/off valve which incorporates a safety feature which facilitates instantaneous isolation of the fuel gas supply to the gas appliance in the event of an emergency. This is due to the fact that the primary and secondary valving members can be selectively decoupled from the drive means for instantaneously urging the primary and secondary valving members into engagement with the primary and secondary valve seats. When a single first magnetic field generating means is provided, the primary and secondary valving members are simultaneously instantaneously decoupled from the drive means when the first magnetic field generating means is powered down, thereby, allowing the primary and secondary valving members to be urged simultaneously into engagement with the corresponding primary and secondary valve seats by the urging means. A further advantage of the invention is achieved when a second magnetic field generating means is provided for magnetically coupling the secondary valving member to the drive means or to the first valving member, and the second magnetic field generating means is independent of the first magnetic field generating means. In which case, the primary and secondary valving members can be independently decoupled from the drive means for selectively closing the respective primary and secondary passageways independently of each other. This aspect of the invention provides a particular advantage when the valve is provided with a main outlet port whereby a fluid supply to the main outlet port is controlled by both the primary and secondary valving means and a fluid supply to the secondary outlet port is controlled by the primary valving means only. In which case, by powering down the second magnetic field generating means only the secondary valving member is decoupled from the drive means for isolating the main outlet port from the fluid supply, while the primary valving member may be retained by the first magnetic field generating means and the drive means for permitting the flow of fluid to the secondary outlet port. Thus, in cases where the valve according to the invention is provided for controlling the supply of fuel gas to a gas powered appliance, if the main outlet port is connected to a main burner of the gas appliance, and the secondary outlet port is connected to a pilot light supply for the main burner, the supply of fuel gas to the main burner can be isolated in the event of an emergency by powering down the second magnetic field generating means, while fuel gas can still be supplied to the pilot light jet through the secondary outlet port.
A further advantage of the invention is that little power is dissipated as heat in the valve, and furthermore, the power requirement of the valve is significantly lower than that which is required by a solenoid operated valve. Furthermore, operation of the valve is relatively silent by comparison to conventional solenoid valves, and the valve is operable for regulating the flow of fluid therethrough without any mechanical hystersis.